This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-273218, filed Sep. 27, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an electronic apparatus incorporating a microcomputer, such as a television receiver. More particularly, the invention relates to an interruption control circuit for restoring such an electronic apparatus from an idling state to a normal operating state.
Television receivers developed in recent years have many functions such as channel-displaying function and multi-screen displaying function. Further, they are designed to display satellite-broadcast programs and audio-multiplexed programs. To perform various functions and display programs of different types, a television receiver incorporates a microcomputer.
FIG. 6 shows a conventional microcomputer section incorporated in a television receiver. As shown in FIG. 6, the microcomputer section comprises a key matrix 101, an A/D converter 105, an input terminal 103, a CPU (Central Processing Unit) 107, and a ROM 109. The input terminal 103 connects the key matrix 101 and the A/D converter 105.
FIG. 7 shows the key matrix 101 in greater detail. The key matrix 101 has switches K1, K2, . . . , Kn and resistors R1, R2, . . . , Rn. The switches K1 to Kn and resistors R1 to Rk are associated with n keys (not shown), respectively. As the switches K1 to Kn are turned on and off, in various combinations, the key matrix 101 generates different voltages.
Assume that one of the keys of the key matrix 101 is pushed. Then, the voltage assigned to the key pushed is applied from the key matrix 101 via the input terminal 103 to the A/D converter 105. The CPU 107 drives the A/D converter 105 in accordance with the program stored in the ROM 109. Thus driven, the A/D converter 105 converts the input voltage to digital data. The digital data is input to the CPU 107. From the digital data the CPU 107 determines which key of the key matrix 101 has been pushed. The CPU 107 controls major components of the television receiver.
The microcomputer section shown in FIG. 6 can accurately determine which key or keys of the key matrix 101 is pushed, no matter when it is pushed.
If the key matrix 101 remains not operated for a prescribed period of time, the television receiver is set into the idle mode. The microcomputer section always stays in the normal mode, however, no matter whether the television receiver is set in the idle mode or the normal mode. Thus, the CPU 107 keeps operating, thus causing the A/D converter 105 functioning. It is therefore determined, at regular intervals, whether the key matrix 101 has been operated or not. Since the CPU 107 keeps operating even if the television receiver stays in the idle mode, the microcomputer section consumes power at all times.
To reduce the power consumption in the microcomputer section, it has been proposed that the CPU 107 be stopped while the television receiver stays in the idle mode, thereby to turn off the A/D converter 105. To set the CPU 107 into the normal mode from the idle mode, an interrupt signal must be supplied to the CPU 107.
To generate an interrupt signal and supply it to the CPU 107, the key matrix 101 must have an additional key. Moreover, the port for supplying the interrupt signal cannot serve for any other purpose.
The present invention has been made in view of the foregoing. The object of the invention is to provide an interruption control circuit for use in an electronic apparatus incorporating a CPU. The interruption control circuit is designed to set the CPU into operation, with ease, whenever necessary, to reduce the power the apparatus consumes while the CPU remains in an idling state.
To achieve the object, the present invention provides an interruption control circuit comprising: a group of key matrices, each having keys and designed to generate different voltages when the keys are operated; an analog-to-digital converter section for converting the voltages applied from the key matrices to digital data; a control section designed to activate the analog-to-digital converter section in an normal mode, deactivate the same in an idle mode, stop operating in the idle mode, and determine, in the normal mode, which key of any key matrix has been pushed, from the digital data supplied from the analog-to-digital converter section; a plurality of buffer circuits for receiving the voltages applied from the key matrices, respectively, each buffer circuit having a threshold voltage and designed to output a first-level signal when the voltage is equal to or higher than the threshold voltage and to output a second-level signal when the voltage is lower than the threshold voltage; a logic circuit for receiving signals output from the buffer circuits and generating a detection signal when the signal output from any one of the buffer circuits changes; and an interrupt-signal generating circuit connected to the logic circuit, for generating a signal for releasing the idle mode and supplying the same to the control circuit when the logic circuit generates the detection signal.
To attain the above-mentioned object, this invention provides an interruption control circuit comprising: a group of key matrices, each having keys and designed to generate different voltages when the keys are operated; an analog-to-digital converter section for converting the voltages applied from the key matrices to digital data; a control section designed to activate the analog-to-digital converter section in an normal mode, deactivate the same in an idle mode, stop operating in the idle mode, and determine, in the normal mode, which key of any key matrix has been pushed, from the digital data supplied from the analog-to-digital converter section; a plurality of buffer circuits for receiving the voltages applied from the key matrices, respectively, each buffer circuit having a threshold voltage and designed to output a first-level signal when the voltage is equal to or higher than the threshold voltage and to output a second-level signal when the voltage is lower than the threshold voltage; a logic circuit for receiving signals output from the buffer circuits and generating a detection signal when the signal output from any one of the buffer circuits changes; an interrupt-signal generating circuit connected to the logic circuit, for generating a signal for releasing the idle mode and supplying the same to the control section when the logic circuit generates the detection signal; and a signal-supplying circuit for supplying the output signals of the buffer circuits to the control section. In this interruption control circuit, the control section selects any key matrix in which at least one key has been pushed, in accordance with the output signals of the buffer circuits, and supplies a selection signal to the analog-to-digital converter section, and the analog-to-digital converter section converts the output voltage of the key matrix to digital data.
To achieve the object described above, the present invention provides an interruption control circuit comprising: a group of key matrices, each having keys and designed to generate different voltages when the keys are operated; an analog-to-digital converter section for converting the voltages applied from the key matrices to digital data; a control section designed to deactivate the same in an idle mode, stop operating in the idle mode, and determine, in a normal mode, which key of any key matrix has been pushed, from the digital data supplied from the analog-to-digital converter section; a plurality of buffer circuits for receiving the voltages applied from the key matrices, respectively, each buffer circuit having a threshold voltage and designed to output a first-level signal when the voltage is equal to or higher than the threshold voltage and to output a second-level signal when the voltage is lower than the threshold voltage; selection circuits connected to output terminals of the buffer circuits, respectively, each for selecting the output signal of the associated buffer circuit in the idle mode; a logic circuit for receiving signals output from the selection circuits and generating a detection signal when the signal output from any one of the buffer circuits changes; an interrupt-signal generating circuit connected to the logic circuit, for generating a signal for releasing the idle mode and supplying the same to the control section when the logic circuit generates the detection signal; and an activating circuit for activating the analog-to-digital converter section in accordance with the detection signal generated by the logic circuit.
In order to achieve the above-mentioned object, the present invention provides an interruption control circuit comprising: a group of key matrices, each having keys and designed to generate different voltages when the keys are operated; an analog-to-digital converter section for converting the voltages applied from the key matrices to digital data; a control section designed to deactivate the same in an idle mode, stop operating in the idle mode, and determine, in a normal mode, which key of any key matrix has been pushed, from the digital data supplied from the analog-to-digital converter section; a plurality of buffer circuits for receiving the voltages applied from the key matrices, respectively, each buffer circuit having a threshold voltage and designed to output a first-level signal when the voltage is equal to or higher than the threshold voltage and to output a second-level signal when the voltage is lower than the threshold voltage; a logic circuit for receiving signals output from the buffer circuits and generating a detection signal when the signal output from any one of the buffer circuits changes; an interrupt-signal generating circuit connected to the logic circuit, for generating a signal for releasing the idle mode and supplying the same to the control section when the logic circuit generates the detection signal; and a channel-selecting circuit for receiving the output signals of the buffer circuits, selecting any key matrix in which at least one key has been pushed, and outputting a selection signal. In this interruption control circuit, the analog-to-digital converter section converts, to digital data, the voltage applied from the key matrices in accordance with the selection signal.
With the present invention it suffices for the user to operate the keys provided in the key matrices, in order to activate the control section. Hence, the key matrices need not have any additional keys for generating interrupt signals. Until any one of the keys provided in the key matrices is pushed, the control section can remain in the idle mode. This helps to reduce the power consumption of the control section.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.